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Author(s): Wade Haaland

Homeostatic Mechanism

The mechanism known as negative-feedback regulation maintains homeostasis. The "receptor, control center, effector" structure of a homeostatic system (described in the previous slide) enables negative-feedback regulation to occur. When a large external change is detected by the receptor, a signal is sent to, and is interpreted by the control center, resulting in a response by the effector to minimize the internal impact of the large external change. This is negative-feedback regulation. The original external change is counteracted internally so that the internal change is small or nonexistent.

Positive-feedback regulation also is seen in biological systems, but it is not utilized for maintaining homeostasis. Rather, positive-feedback is used to augment a change within an organism. For example, during birth, the uterus contracts to expel the infant. Positive-feedback causes these contractions to continue until the birth is complete. So, whereas negative-feedback helps homeostatic systems to remain fairly constant by responding to changes in the external environment, positive-feedback promotes the change.